A saddle-ridden type vehicle such as a motorcycle is provided with a supercharger and air compressed by the supercharger is supplied to a combustion chamber of an engine, so that it is possible to increase a thermal efficiency and an output of the engine. Patent Document 1 discloses a saddle-ridden type vehicle having a supercharger.
The saddle-ridden type vehicle disclosed in Patent Document 1 has an air cleaner configured to purify exterior air, a supercharger configured to compress the air purified by the air cleaner, an intercooler configured to cool the air of which a temperature has increased resulting from the compression by the supercharger, and a surge tank configured to temporarily store therein the air cooled by the intercooler and to supply the same to an engine. Also, in the saddle-ridden type vehicle, the air cleaner and the supercharger are interconnected by an air intake piping. Also, the supercharger and the intercooler are interconnected by an air outlet piping. Also, the intercooler and the surge tank are disposed adjacent to each other and are directly connected via a short pipe line.
Further, the saddle-ridden type vehicle disclosed in Patent Document 1 has an air bypass piping configured to allow the compressed air downstream of the supercharger to escape toward an upstream side of the supercharger without flowing the compressed air in the supercharger and an air bypass valve configured to open and close the air bypass piping. The air bypass piping and the air bypass valve have a function of escaping the compressed air downstream of the supercharger toward the upstream side of the supercharger to prevent a pressure in the air outlet piping downstream of the supercharger from excessively increasing when a throttle valve configured to adjust an inflow amount of air intake to the engine is completely closed.
In the saddle-ridden type vehicle disclosed in Patent Document 1, the air cleaner is disposed at a lower-rear side of the engine, the supercharger is disposed at a lower-front side of the engine and the intercooler and the surge tank are disposed at the rear of the engine. The air intake piping extends in a front-rear direction at a lower-left side of the engine, and the air outlet piping extends in the front-rear direction with traversing laterally a cylinder or cylinder head of the engine.
Also, the air bypass valve is positioned at the rear of a left side of the supercharger and at the front of a left side of a crank case and is provided at a substantially intermediate position of the air intake piping. Also, the air bypass valve is positioned at an inner side of the saddle-ridden type vehicle relative to the air intake piping. Also, the air bypass piping is disposed in front of the left side of the crank case (refer to an air bypass valve 36 and an air bypass hose 37 in FIG. 9 of Patent Document 1).
Patent Document 1: Japanese Patent Application Publication No. 2015-78634A
In a vehicle including an engine having a supercharger, when the air bypass valve opens, the air flows from the downstream side toward the upstream side of the supercharger via the air bypass valve, so that an air shooting sound “shoo” is generated. The air shooting sound is a sound inherent to the engine having the supercharger and is one of charms of the engine having the supercharger.
In the saddle-ridden type vehicle disclosed in Patent Document 1, since the air bypass valve is disposed at a position corresponding to a lower part of the crank case of the engine and the air bypass valve is located at a low position, a head of a driver sitting on a seat of the saddle-ridden type vehicle and the air bypass valve are spaced from each other. As a result, it is difficult for the driver to hear the air shooting sound upon the opening of the air bypass valve.
Also, the air bypass valve is disposed at the inner side of the saddle-ridden type vehicle relative to the air intake piping, so that it is located at a position below the engine, as seen from the driver sitting on the seat of the saddle-ridden type vehicle. For this reason, the engine is interposed between the head of the driver and the air bypass valve, so that it is difficult for the air shooting sound to reach ears of the driver upon the opening of the air bypass valve.
Also, in order to express the charms of the engine having the supercharger, the air bypass valve is preferably disposed at a position at which it can be easily seen from an outside. Regarding this, according to the saddle-ridden type vehicle disclosed in Patent Document 1, since the air bypass valve is disposed below the engine and at the inner side of the saddle-ridden type vehicle, the air bypass valve is difficult to be seen from the outside.
In the meantime, it is necessary to protect the air bypass valve from collision with flying stones during traveling.
Patent Document 2 also discloses a saddle-ridden type vehicle having a supercharger.
The saddle-ridden type vehicle disclosed in Patent Document 2 has an air cleaner configured to purify exterior air, a supercharger configured to compress the air purified by the air cleaner, an intercooler configured to cool the air of which a temperature has increased resulting from the compression by the supercharger, and a surge tank configured to temporarily store therein the air cooled by the intercooler and to supply the same to an engine. Also, in the saddle-ridden type vehicle, the air cleaner and the supercharger are interconnected by an air intake piping. Also, the supercharger and the intercooler are interconnected by an air outlet piping. Also, the intercooler and the surge tank are disposed adjacent to each other and are directly connected via a short pipe line.
Patent Document 2: Japanese Patent Application Publication No. 2015-74242A
The saddle-ridden type vehicle configured to compress the air by the supercharger and to supply the same to the engine has more components of an intake system, as compared to natural intake, because the supercharger, the intercooler, the air outlet piping configured to interconnect the same, and the like are provided. Also, in the supercharger (turbocharger) configured to drive a turbine by using an exhaust gas of the engine, it is necessary to smoothly supply the exhaust gas to the turbine of the supercharger. Therefore, it is preferably to dispose the supercharger in the vicinity of an exhaust port provided at a front part of the engine. Due to this, the supercharger is disposed in front of the engine in many cases. On the other hand, since an intake port of the engine is provided at a rear part of the engine, the surge tank configuring a downstream-side of the intake system is disposed at the rear of the engine in many cases. Further, an arrangement place of the air cleaner is limited due to a relation with a layout of a path (a duct and the like) configured to guide the exterior air, which is to be used for combustion of fuel, to the air cleaner. Also, an arrangement place of the intercooler is limited due to a relation with a layout of a path configured to guide the exterior air, which is to be used for cooling of the compressed air, to the intercooler. Due to the situations, in the saddle-ridden type vehicle having the supercharger, it is difficult to determine arrangement of the components of the intake system and the intake pipings configured to interconnect the components around the engine.
In the saddle-ridden type vehicle of Patent Document 2, the air cleaner is disposed at a lower-rear side of the engine, the supercharger is disposed at a lower-front side of the engine, and the intercooler and the surge tank are disposed at the rear of the engine. Also, the air inlet piping configured to interconnect the air cleaner and the supercharger is piped at a side below the engine and the piping configured to interconnect the supercharger and the intercooler traverses laterally the cylinder or cylinder head of the engine.
When it is intended to improve a design property of the saddle-ridden type vehicle, an outward appearance of the engine as seen from a side is important. When the air outlet piping traverses laterally the cylinder or cylinder head of the engine, like the saddle-ridden type vehicle of Patent Document 2, the outward appearance of the engine as seen from a side is deteriorated, so that the design property of the saddle-ridden type vehicle may be lowered.
Also, when the air intake piping or the air outlet piping is disposed at the side of the engine, like the saddle-ridden type vehicle of Patent Document 2, the traveling wind is difficult to collide with the side of the engine, so that it is difficult to sufficiently cool the engine. Also, when the piping is disposed at the side of the engine, an empty space at the side of the engine is reduced, so that it is difficult to secure a space for disposing the components at the side of the engine. Also, when the piping is disposed at the side of the engine, a vehicle width of the saddle-ridden type vehicle increases, so that a lightsome handling property of the saddle-ridden type vehicle may be deteriorated.